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<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>03JS数据类型</title>
</head>
<body>
<script>
    //JS数据类型 = 原始类型 + 引用类型
    //原始类型:number string boolean null undefined
    var a = 1;
    var b = 9.9;
    console.log(a, typeof a, b, typeof b);
    var c = '你好';
    var d = "你好";
    console.log(c, typeof c, d, typeof d);
    var e = true;
    var f = false;
    console.log(e, typeof e, f, typeof f);
    //声明了变量但未赋值,会得到undefined,未定义型
    var g;
    console.log(g, typeof g);

    //引用类型 Object Number String Boolean Array...
    //1)自定义JS对象
    let obj = {
        name: '张三',
        age: 18
    };
    console.log(obj, typeof obj);//{name: '张三', age: 18} 'object'
    console.log(obj.name,obj.age);//张三 18

    obj.age = 19;
    console.log(obj);//{name: '张三', age: 19}

    /* 给对象动态新增一个like属性 */
    obj.like = '吃火锅';
    console.log(obj);//{name: '张三', age: 19, like: '吃火锅'}
    console.log(obj.like);//'吃火锅'
    console.log(obj.play);//undefined 访问对象不存在的属性会得到undefined

    //JS数组
    let arr = ['李逵','鲁班','露娜',1,6.6,false];
    console.log(arr,typeof arr);
    console.log(arr[0]);
    console.log(arr[5]);
    console.log(arr[99]);//访问数组不存在的下标,会得到undefined
</script>
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